Add support for long-to-double in the optimizing compiler.

- Add support for the long-to-double Dex instruction in the
  optimizing compiler.
- Enable requests of temporary FPU (double) registers during
  code generation.
- Fix art::x86::X86Assembler::LoadLongConstant and extend
  it to int64_t values.
- Have art::x86_64::X86_64Assembler::cvtsi2sd work with
  64-bit operands.
- Generate x86, x86-64 and ARM (but not ARM64) code for
  long to double HTypeConversion nodes.
- Add related tests to test/422-type-conversion.

Change-Id: Ie73d9e5e25bd2e15f585c371e8fc2dcb83438ccd
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 3689452..c482885 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -1429,6 +1429,13 @@
           break;
 
         case Primitive::kPrimLong:
+          // Processing a Dex `long-to-double' instruction.
+          locations->SetInAt(0, Location::RequiresRegister());
+          locations->SetOut(Location::RequiresFpuRegister());
+          locations->AddTemp(Location::RequiresFpuRegister());
+          locations->AddTemp(Location::RequiresFpuRegister());
+          break;
+
         case Primitive::kPrimFloat:
           LOG(FATAL) << "Type conversion from " << input_type
                      << " to " << result_type << " not yet implemented";
@@ -1608,7 +1615,37 @@
           __ cvtsi2sd(out.As<XmmRegister>(), in.As<Register>());
           break;
 
-        case Primitive::kPrimLong:
+        case Primitive::kPrimLong: {
+          // Processing a Dex `long-to-double' instruction.
+          Register low = in.AsRegisterPairLow<Register>();
+          Register high = in.AsRegisterPairHigh<Register>();
+          XmmRegister result = out.As<XmmRegister>();
+          XmmRegister temp = locations->GetTemp(0).As<XmmRegister>();
+          XmmRegister constant = locations->GetTemp(1).As<XmmRegister>();
+
+          // Binary encoding of 2^32 for type double.
+          const int64_t c1 = INT64_C(0x41F0000000000000);
+          // Binary encoding of 2^31 for type double.
+          const int64_t c2 = INT64_C(0x41E0000000000000);
+
+          // low = low - 2^31 (to prevent bit 31 of `low` to be
+          // interpreted as a sign bit)
+          __ subl(low, Immediate(0x80000000));
+          // temp = int-to-double(high)
+          __ cvtsi2sd(temp, high);
+          // temp = temp * 2^32
+          __ LoadLongConstant(constant, c1);
+          __ mulsd(temp, constant);
+          // result = int-to-double(low)
+          __ cvtsi2sd(result, low);
+          // result = result + 2^31 (restore the original value of `low`)
+          __ LoadLongConstant(constant, c2);
+          __ addsd(result, constant);
+          // result = result + temp
+          __ addsd(result, temp);
+          break;
+        }
+
         case Primitive::kPrimFloat:
           LOG(FATAL) << "Type conversion from " << input_type
                      << " to " << result_type << " not yet implemented";